High electron mobility transistors (HEMTs) are utilized in integrated circuits for high-frequency applications due to their high efficiency relative to other power semiconductor devices such as insulated gate bipolar transistors and thyristors. HEMTs utilize a heterojunction between two semiconducting materials with different band gaps to form a device channel, instead of a doped region as in a metal oxide semiconductor field-effect transistor (MOSFET). Two exemplary materials used to form the heterojunction within a HEMT are a doped wide-bandgap n-type donor layer of AlGaN coupled to an un-doped narrow-bandgap channel layer of GaN. Ohmic contacts formed to the AlGaN donor layer are subject to increased contact resistance as the Al concentration of the AlGaN donor is increased. Conversely, reducing the concentration of the AlGaN donor layer improves the contact resistance, but degrades electron mobility within the channel.